it's what makes a subaru, a subaru. >>> welcome back to "starting point," everyone. live here from boston, behind me what was the crime scene, boylston street, now open for business for the first time. since the bombings. this morning investigators are looking into tamerlan tsarnaev's online influence, asking a lot of questions, including whether an al qaeda in yemen website helped him to build the bombing. here's cnn's david mattingly. >> reporter: i-witness photographs capture the violent street shoot-out and the last moments of a desperate and dangerous tamerlan tsarnaev. a federal law enforcement source tells cnn tsarnaev's own brother conveyed to investigators he was not only the mastermind behind the boston bombings, but he was motivated by a jihadist call for retaliation for so-called attacks on islam. a self-made radical, with a wealth of information at his fingertips. >> estimate there are over 8,000 websites that are -- that have very extremist radical ideology. >> reporter: 8,000? >> over 8,000 websites. >> reporter: she studies the reach and impact of onl